Electrical connector assembly

ABSTRACT

A load-break electrical connector assembly including a plug-in cable connector having a probe which includes a first electrical conductor, and a bushing assembly which includes a second conductor adapted to engage the first conductor of the cable connector. A magnetic clamp is disposed in the bushing assembly which prevents removal of the cable connector from the bushing assembly when the magnitude of current flowing through the first and second electrical conductors exceeds a predetermined magnitude.

United States Patent I 1151 3,670,287 Keto 14 1 June 13, 1972 [54] ELECTRICAL CONNECTOR ASSEMBLY 3,390,559 7/1968 Steutzer ..70/275 [72] Inventor: August I. Keto, Sharpsville, Pa. FOREIGN PATENTS OR APPLICATIONS 1 1 Assisnw Westinghouse Electric Corporation, Pitt- 1,234,303 3/1960 France ..339/3o sburgh, Pa.

Primary Examiner-Marvin A. Champion [22] Flled' 1970 Assistant Examiner-Robert A. Hafer [21] Appl. No.: 64,383 Attorney-A. T. Stratton, F. E. Browder and D. R. Lackey 57 ABSTRACT [52] U.S. Cl. ..339/12 R, 339/82, 339/91 P J [51] Int. Cl ..Hlr 11/30 A l k lectri al connector assembly including a plug- 58 Field of Search ..339/12, 30, 79, 82, 1 1 1, 74, in cable connector having a Probe which includes first elec- 339/75 0 trical conductor, and a bushing assembly which includes a second conductor adapted to engage the first conductor of the f C-ted cable connector. A magnetic clamp is disposed in the bushing [56] Re I assembly which prevents removal of the cable connector from UNITED STATES PATENTS the bushing assembly when the magnitude of current flowing through the first and second electrical conductors exceeds a 2,758,291 8/1956 RlChaldS 339/94 predetermined magnitude 3,474,386 /1969 Link ...339/60 R 1,797,581 3/1931 Kuhn et a1. ..339/30 Claims, 5 Drawing Figures I6 92 1 96 I12 liq 114 PA'TENTEDJUH 13 m2 SHEET 10F 2 INVENTOR Augusf I. Keto ATTORNEY BACKGROUND OF THE INVENTION shielded cables of he electrical distribution system to be quickly connected t or disconnected from, electrical apparatus such as distribution transformers and electrical switches. The early plug-in cable connectors were non-load break devices, with the load-break capability being supplied by auxiliary load-break switches. While auxiliary load-break switches are acceptable functionally, they add substantially to the cost of the underground distribution system and thus plugin type electrical connector assemblies were developed which have load break capability. For example, copending application Ser. No. 1,828, filed Jan. 9, 1970, which is assigned to the same assignee as the present application, discloses a plug-in electrical connector having load-break capabilities. The term load-break capability," as used in this specification, also signifies load-make and fault close-in capabilities.

To provide a plug-in type electrical connector assembly with load-break capability, and also fault close-in capability, the are drawn upon breaking the load current must be quickly and effectively extinguished, and the arc and gas pressures created when coupling the connector portions while a fault exists must be contained without catastrophic damage to the apparatus and without hazard to the operating personnel. Since plug-in load-break connectors of this type are used on systems with current limiting protection, such as fuses or circuit breakers, between the cable termination and the high voltage feeder, the fault close-in requirements of the bushing assembly may be predetermined.

7 Load break electrical connector assemblies must include means for interrupting the electrical are drawn between the separating electrical conductor portions of the plug-in cable connector and bushing, when the electrical connector assembly is disassembled while load current is flowing. This is accomplished by providing the plug-in cable connector and bushing with cooperative insulating sleeve and rod members, commonly referred to as the quench tube and snuffer rod, respectively, which members are formed of arc extinguishing materials. The quench tube and snufi'er rod are disposed to confine and squeeze the are drawn between the separating electrical conductors, with the surfaces of the quench tube and snuffer rod decomposing under the influence of the hot are, generating gases which cool, deionize and blow out the arc.

Most load-break electrical connector assemblies in use today are manually operated by an operator with a hot stick, as they are relatively simple in construction, low in cost, and they perform very reliably. The simple operating requirement of sliding the plug-in cable connector into the bushing assembly com letes the electrical circuit between the probe contact of the cable connector and the pressure type contact of the bushing assembly, and the reverse operation breaks the circuit. The necessary clearances are provided to promote the smooth and effortless operation. However, on fault close-in, the effortless close-in operation may be defeated, as internal pressures are created which may blow-back the cable connector, and defeat the intended operation. The smoother and easier the close-in, the more likely blow-back will occur on a fault close-in.

It would be desirable to provide a new and improved manually operable load-break electrical connector assembly which eliminates the blow-back problem associated with such connectors of the prior art when they are closed on a fault. Further, it would be desirable to provide a connector assembly having this non-blowback feature, while still providing the smooth, effortless operation associated with prior art loadbreak electrical connectors.

SUMMARY OF THE INVENTION Briefly, the present invention is a new and improved circuit interrupter of the plug-in electrical connector type, having a plug-in portion adapted for connection to shielded electrical cable, and a bushing assembly which is adapted for mounting on the casing of electrical apparatus, such as a distribution transformer. The connector assembly has load-make and break, and fault close-in capabilities, provided by cooperative quench tube and snuffer rod members disposed in the plug-in and bushing portions of the connector, respectively, which members are formed of arc-extinguishing materials.

Blow-back of the plug-in connector on fault close-in is eliminated by protective means which includes an automatically operated magnetic clamp disposed in the bushing assembly, which is actuated when the magnitude of the current flowing-through the bushing exceeds a predetermined value, such as full load current plus a reasonable overload. The magnetic clamp, when actuated, reduces the dimensions of its aperture, preventing withdrawal of the probe contact on the plug-in cable connector from the bushing assembly.

BRIEF DESCRIPTION OF THE DRAWINGS The invention may be better understood, and further advantages and uses thereof more readily apparent, when considered in view of the following detailed description of exemplary embodiments, taken with the accompanying drawings, in which:

FIG. 1 is an elevational view, partially in section, of an electrical connector assembly constructed according to a first embodiment of the invention;

FIG. 2 is a perspective view of the quench tube and magnetic clamp used in the electrical connector assembly shown in FIG. 1;

FIG. 3 is an elevational view, partially in section, of an electrical connector assembly constructed according to another embodiment of the invention;

FIG. 4 is a perspective view of the quench tube and magnetic clamp used in the electrical connector assembly shown in FIG. 3; and

FIG. 5 is an elevational view, partially in section, of an electrical connector assembly constructed according to still another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and FIG. 1 in particular, there is shown an elevational view, partially in section, of an electrical connector assembly 10 constructed according to the teachings of the invention. Electrical connector assembly 10, which is broadly an electrical circuit interrupter, includes first and second cooperative portions which have first and second conductor means between which an electrical arc is formed, with are confining and extinguishing means disposed to confine and extinguish the are. More specifically, connector assembly 10 includes a first portion including a plug-in cable connector 12, and a second portion including a bushing assembly 14, which when assembled provide a sealed electrical connection. The plug-in cable connector 12 is adapted for connection to a shielded electrical cable, and bushing 14 is adapted for mounting through an opening in the casing of electrical apparatus, such as a distribution transformer.

Cable connector 12 includes a hood portion 16 and amain body portion 22, both formed of resilient material such as an elastomer, with the hood portion 16 being molded to define a cavity 18 sized to snugly receive the upper portion of bushing assembly 14. In other words, the plug-in cable connector and bushing portions have complementary surfaces, which enclose and seal an electrical connection made between their conductors. Cable connector 12 also includes an electrical conductor which has one end connected to the conductor portion of the shielded electrical cable (not shown) within the main body portion 22 of the cable connector 12, and its other end is part of the probe assembly 23 which extends coaxially into cavity 18. The probe assembly 23 also includes an insulating rod member 24, called the snuffer rod, which is secured to the lower end of conductor 20. Conductor 20 has first and second diameters 25 and 27, respectively, which provide a shoulder 29 at their junction, for purposes which will be hereinafter explained. The second diameter 27 is larger than the first, and it starts at the outwardly extending end of conductor 20. Conductor 20 and snuffer rod 24 have the same diameters at their junction, providing a smooth transition from the insulating rod 24 to the conductor 20. The snuffer rod 24 is formed of an arc extinguishing material, with methyl methacrylate filled with glass fibers being an excellent material, as disclosed in my copending application Ser. No. 1,827 filed Jan. 9, 1970, which is assigned to the same assignee as the present application, but other are extinguishing materials may be used if desired. The lower end 26 of snufi'er rod 24 may be curved or rounded to facilitate its introduction into the bushing assembly 14. Conductor 20 may join the conductor of the shielded cable at a 90 angle, as shown, in which case connector 12 is commonly referred to as an elbow," or conductor 20 may be a coaxial continuation of the shielded conductor, as required by the specific application. A portion of the resilient housing of connector 12 may be formed of a conductive material, such as conductive rubber, which is adapted to contact the shield of the shielded cable, and continue the cable shield to the casing of the apparatus when the connector is assembled with the bushing assembly.

The bushing assembly 14 includes a cylindrical elongated insulating body member 28 which is preferably formed of a rigid solid insulating system, a conductive sleeve or tubular member 30, a terminal stud 32, a replaceable contact member 34, an insulating sleeve member 36, commonly called the quench tube, which is formed of arc confining and extinguishing material and which may be the same material of which the snuffer rod 24 is formed, and a metallic mounting ring assembly 38.

The body member 28 has first and second ends 40 and 42, respectively, with an aperture 44 extending between its ends. Body member 28 may be cast or molded of any suitable resinous insulation system which possesses the following characteristics. It must be a good electrical insulator, it must be weather resistant, crack resistant, rigid but not brittle, it must possess a high physical strength at ambient and elevated temperatures, and it must have a coefficient of thermal expansion which closely matches the coefiicient of thermal expansion of the tubular conductive member 30. Body member 28 is preferably cast, instead of molded, because of the superior strength of cast resinous insulation systems over molded systems. In general, the filled epoxy cast resin systems will provide the desired characteristics, with the filler being selected to match the coefficient of thermal expansion of the filled system to that of the metallic conductor or insert. A finely divided filler formed of beryllium aluminum silicate has been found to be excellent in matching the coefficient of thermal expansion of the filled epoxy resin system to copper, but other fillers may be used, such as quartz or silica. For 7,200 volt applications where the encased end of a bushing assembly is disposed in oil, or other insulating dielectric fluid, fillers for providing arc and track resistance are not required. If the encased end is to be operated in air, finely divided alumina trihydrate (Al,O -3H O), may be added to obtain the desired arc and track resistance.

Conductive sleeve member is preferably formed of a thin wall tube, constructed of a good electrical conductor, such as copper, with the tube having first and second ends 45 and 46, respectively, and an aperture 48. The aperture 48 has a uniform diameter except for a shoulder or step 50 which reduces the diameter of the aperture for a short longitudinal dimension at a predetermined location intermediate the first and second ends 45 and 46, respectively, of the conductive sleeve member 30.

The wall of the aperture 48 is threaded, starting at the first end 45 of the conductive sleeve member 30 and extending to the location of shoulder 50. When using a thin wall tube, threads 52 in the inner diameter of the conductive sleeve member 30 may be obtained by rolling threads on the outside surface of the tube.

The second end 46 of conductive sleeve or tubular member 30 is hermetically sealed with a terminal stud 32, which is also formed of copper, or other good electrical conductor, and is adapted for connection to encased electrical apparatus, such as the high voltage winding of a distribution transformer. Terminal stud 32 includes a portion 54 having a diameter selected to snugly fit the diameter of aperture 48 of the conductive sleeve member 30, with portion 54 being secured within the aperture 48, such as by a silver solder bead, which-electrically connects terminal stud 32 to conductive sleeve member 30, and also hermetically seals end 46 of conductive sleeve member 30. Portion 54 of terminal stud member 32 also includes an outwardly extending portion 56 which is adapted to receive an electrical lead and fastening means, such as a nut.

As illustrated in FIG. 1, conductive sleeve member 30 is sealingly disposed in the aperture 44 of body member 28, with its first end 45 starting within the aperture 44 a predetermined dimension from the first end 40 of body member 28, and with its second end 46 being substantially aligned with the second end 42 of body member 28.

The metallic mounting ring assembly 38 includes a flange portion 60 embedded within the cast body portion 28, an outwardly extending disc or ring portion 58, and a plurality of spaced extensions, such as extensions 62 and 64, which, along with the flange portion 60, extend toward the first end 40 of the body member 28, and which have openings for receiving clips disposed on the cable termination to mechanically secure the cable connector in assembled relation with the bushing 14.

The embedded flange 60 of mounting ring member 38 extends upwardly from the disc or ring portion 58, toward the first end 40 of body member 28, forming a smooth cylindrical surface coaxial with the axis of the conductive sleeve member 30. The flange portion 60 may be of any suitable longitudinal length, and in addition to providing a strong mechanical bond with the body member 28, it also functions as a ground shield providing a smooth, equipotential surface which is connected to the metallic case or enclosure of the associated apparatus.

Mounting ring member 38 may be formed of any suitable material, such as steel, and it may be welded to the casing of the associated electrical apparatus. For example, bushing 14 may be inserted into an opening 66 in a metallic casing 68, with the ring portion 58 of the mounting ring member 38 resting against the casing 68. The mounting ring member 38 may then be welded to the casing 68, as illustrated by the welding bead 67. Or, if it is not desirable to permanently mount the bushing within an opening of its associated apparatus, a suitable gasket member (not shown) may be disposed between the portion 58 of mounting member 38, and the casing 68, and the bushing 14 secured in place by a conventional spring and flange assembly (not shown), disposed on the encased end of bushing 14. A circumferential groove (not shown) may be disposed about body member 28 to receive the spring member of the spring and flange type mounting assembly.

In forming body member 28 of bushing 14, it is necessary to properly position the conductive sleeve member 30 and mounting ring member 38 within the casting mold, prior to the introduction of the casting resin system. In order to preclude an air leak between the inside of casing 68 and the atmosphere, about the embedded portion of the mounting ring member 38, due to non-adhesion of the cast resin system to the embedded portion of the mounting ring member 38, which may develop due to the welding heat if the ring member 58 is welded to the casing 68, or due to differences in the coefficient of thermal expansion of the mounting ring member 38 and body member 28, a coating 70 of resilient material may be disposed on the flange 38. For example, as disclosed in US. Pat. No. 3,504,106, which is assigned to the same assignee as the present application, the coating may be a thermoplastic material, such as a linear, saturated polyester resin system. This material will adhere to the flange 60 and also the cast resin system providing a hermetic seal between the mounting ring member 38 and the cast body portion 28.

A coating 72 of material similar to the material of coating 70, may be disposed about the conductive sleeve member 30 for a predetermined longitudinal dimension, prior to its being embedded in the body member 28, in order to ensure that an oil seal has been obtained between the conductive sleeve members 30 and body member 28.

Contact member 34 is formed of a tubular conductor, such as copper, having an externally threaded portion 82 sized to cooperate with the threads 52 on the inside diameter of conductive sleeve member30, and a pressure terminal portion 84 which has an outside diameter slightly smaller than the inside diameter of the conductive sleeve member 30, to provide a predetermined space between the pressure terminal portion 84 and conductive sleeve members 30 when the threaded portion 82 is threadably engaged with the conductive sleeve member 30. Contact member 34 is inserted into the conductive sleeve member 30 and rotated, using a tool designed for this purpose, until the end of the threaded portion is turned tightly against shoulder 50, to provide a good electrical contact between contact member 34 and the conductive sleeve member 30.

The pressure terminal portion 84 of contact member 34 may be longitudinally slotted to provide a plurality of upwardly extending finger portions, which extend toward the first end 45 of conductive sleeve member 30 when assembled therewith. The outside diameter of pressure terminal portion 84 is reduced near its extreme end, and a spring member 86 is provided which is circumferentially disposed about the finger portions to maintain the desired inside diameter of the openin g in the contact member 34, and provide a good tight electrical connection between the fingers and electrical contact 20 of the cable connector 12, when the electrical contact 20 of the cable connector 12 extends into the opening defined by the inside surfaces of the contact fingers.

If the plug-in cable connector 12 is of the type which terminates the cable shield, with the ground return conductors of the cable being twisted together and connected to a suitable terminal on the casing 68, and a corona extinction voltage within system requirements is obtained, the connector assembly will not require means for continuing the cable shield to the casing 68'. If the plug-in cable connector 12 is of the type which requires the bushing to continue the cable shield to the casing 66, a metallic coating 91, such as sprayed aluminum, may be disposed about the body member 28, starting between the shoulder 80 and mounting ring member 26, and continuing along body member 28 for a predetermined dimension.

The quench tube member 36 has first and second ends 90 and 92, respectively. Quench tube member 36 has a threaded portion 96 which cooperates with the internal threads 52 of conductive sleeve member 30. Adjacent the first end 45 of conductive sleeve member 30, the arc confining and extinguishing quench tube member 36 steps outwardly to a surface 98 which snugly fits the aperture 44 of insulating body member 28. The quench tube 36 again steps outwardly at the first end 40 of body member 28, providing a shoulder which rests against the first end 40 to limit the inward'travel of quench tube 36 and properly locate its inner end 92. The outer surface of quench tube 36 may then flare smoothly outward from the shoulder, and provide a smooth radius into its outer end 90 for receiving and cooperating with the plug-in connector 12.

A sealant and lubricant, such as silicone grease, should be used to insert quench tube 36 into cooperative engagement with conductive sleeve member 30, to seal the small clearances between the quench tube 36 and the adjacent inner wall of the insulating body member 28. This will prevent an are from following this path to the outer surface of bushing member 14, where it may proceed to ground.

In the operation of the electrical connector 10, the plug-in cable connector 12 should be coupled with bushing 14 with a positive action which will bring the conductor 20 of the cable connector 12 into rapid, positive contact with the pressure terminal 84. If there is a fault in the apparatus at which connector 10 is associated, or in its connected load, ionized gas is produced by the resulting arc between the conductors of connector 12 and bushing assembly 14, which tends to blow-back the connector 12, defeating the closure attempt. The force of the blow-back is reduced by chamber 102, disposed between contact 34 and terminal 32, but it would be desirable to completely eliminate the possibility of blow-back. Chamber 102 is defined by the inside wall of conductive sleeve member 30, starting at the lower end of contact member 34 and terminating at end 103, a predetermined distance from the lower end of contact member 34. Excess volume in conductive sleeve member 30, from end 103 to tenninal 32, is filled with means 105. Means 105 may be conductive or insulating, as desired. Chamber 102 provides space for ionized gases to expand, cool and condense. The surge or expansion chamber 102 also makes it unnecessary to vent the ionized gases to the inside of casing 68 through a one-way pressure release seal. Thus, the desired insulating level of the fluid dielectric disposed within casing 68 is maintained, and possible flashover within the casing from a live part to ground is also precluded, since ionized gas is not released to the inside of casing 68. The surge chamber 102 contains the ionized gases until they condense and cool, to reduce their vapor pressure.

When the plug-in cable connector 12 is decoupled from the bushing assembly 14 during normal load conditions, for example up to 200 amperes in a 7,200 volt circuit, an arc will be drawn between the ends of the contact fingers of the pressure terminal 84 and terminal 20 of plug-in connector 12, with the are being drawn between the snuffer rod 24 and the quench tube 36. The heat of the arc will liberate deionizing gases from the snuffer rod 24 and quench tube 36, with the gases deionizing and blasting the arc to effect an early extinction thereof. Tests have shown that an are drawn in a 7,200 volt circuit in which a load current of 200 amperes is flowing is extinguished within one-half to one cycle. In the extinction function, the snuffer rod 24 and quench tube 36 squeeze, stretch and cool the are, as well as deionize and blast the are by liberating gases. In the prior art, the end of the quench tube 36 is disposed immediately adjacent the upper end of the pressure terminal 84, but in the embodiment of the invention shown in FIG. 1, end 90 of the quench tube 36 is spaced from the pres sure terminal 84, for reasons which will be hereinafter disclosed.

If there is a low impedance fault in the load upon closing or coupling the cable connector 12 with the bushing assembly 14, protective current limiting means, such as fuses or breakers in the high voltage cable feeders, will clear the circuit and limit the maximum current to the fault close-in rating of the electrical connector, such as 10,000 amperes in a 7,200 volt circuit. The 10,000 ampere fault current, however, may develop a back pressure, due to heat and ionized gases, which is sufficient to overcome the closing force applied by the operator with the hot stick, blowing back the connector with possible hazard to the operating personnel. This invention precludes such an occurrence by providing protective means which is automatically brought into operation by the flow of fault current, to clamp the probe 23 and prevent its withdrawal from the bushing assembly 14.

FIG. 1 illustrates protective means 110, which, as illustrated more clearly in the perspective view of FIG. 2, includes first and second metallic segments 112 and 114. Segments 112 and 114 are formed of a magnetic material having a high permeability and a low retentivity, such as soft iron. Segments 112 and 114 are each substantially semi-circular in general crosssection, and they are disposed in bushing assembly 14 between the pressure terminal 84 and the quench tube 36, such that they form a tubular, cylindrical electromagnet about conductor 20 when connector 12 is plugged into bushing assembly 14, with conductor 20 functioning as a one turn coil and segments 112 and 114 as the iron core of an electromagnet, very similar to an electromagnet of the horseshoe type.

The flat faces of one segment are aligned with similar faces on the other segment. For example, the flat faces 116 and 1 18 on segment 114, are aligned with the flat faces on segment 112, but the aligned faces are spaced therefrom by a predetermined dimension 120. When spaced by this dimension, the segments 112 and 114 define an aperture 122 which has sub stantially the same diameter as the aperture through the quench tube 36, as illustrated in FIG. 2, with the end 92 of the quench tube being in contact with the upper ends of the two segments or very close thereto, not exceeding about 0.020 inch.

The spacing 120 between the segments 112 and 114 is maintained by suitable biasing or resilient means disposed between their adjacent aligned faces, such as indicated generally at 124 and 126. Resilient means 124 and 126 may be small coil springs, or any other suitable resilient spacing means may be used, such as small leaf springs.

The outer surfaces of segments 112 and 114 are threaded, such as with threads 128 on segment 112, enabling the resulting protective assembly 1 to be properly positioned in bushing assembly 14 by turning it into the tubular conductive sleeve member 30, after the contact member 34 has been threadably inserted into conductive means 30. The threads on the outer surfaces of these segments also enable these segments to be removed and replaced, during any required maintenance procedures. The lower end of protective assembly 110 is spaced from the pressure terminal 84, with the spacing not being critical, such as about 0.020 inch.

The two diameters 25 and 27 of the probe 23, the longitudinal length dimension of the protective assembly 110, the cross-sectional area of the flat surfaces or poles of the segments, and the spacing 120 between the adjacent poles or faces of the segments 112 and 114, are selected such that when the current flowing through conductor 20 exceeds a predetermined magnitude, the force of the resilient means, such as means 124 and 126, in maintaining the spacing 120 between the segments 112 and 114 is overcome by the mutual attraction of the segments 112 and 114. The dimensions of the aperture 122 through protective means 110 are changed when gap 120 is reduced, providing a dimension across aperture 122, in a direction perpendicular to the faces of the segments which is less than the diameter 27 of the probe 23. The electromagnet or protective assembly 110 has a threshold, similar to the pick-up point of an electromagnetic relay, with the threshold, by design, being greater than the normal current rating of the electrical connector 10, such as 200 amperes in a 7,200 volt circuit, plus a predetermined overload. Beyond the current rating plus overload, the protective assembly 110 will be actuated to prevent withdrawal of the probe 23. The desired threshold value may be obtained by properly selecting the gap dimension 120 and area of the poles, with the attractive force between the segments when saturated, being directly proportional to the first power of the pole area, directly proportional to the current magnitude, and inversely proportional to the air gap dimension or spacing between the poles.

Bushing 14 thus includes a body member 28, a mounting ring 38, a conductive sleeve member 30, and a terminal stud member 32, which components are permanently assembled. The remaining components, i.e., contact member 34, the electromagnetic or protective means 110, and the arc confining and extinguishing tubular sleeve member 36, are all replaceable.

ln the operation of the electrical connector 10 shown in FIG. 1, the operator, using a hot stick, plugs connector 12 into bushing 14 with a force which firmly seats connector 12 in assembled relation with the bushing assembly 14. If there is a fault in the connected load, the resultant arcing between the contacts upon closure may produce pressures which attempt to blow-back the connector 12. However, pressures of this magnitude will only be produced by currents of sufficient value to actuate protective means 110. Protective means reduces the dimensions of its aperture 120, preventing withdrawal of the probe 23 when the shoulder 29 of the probe strikes the protective means 1 10.

In addition to preventing blow-back of connector 12, protective means 1 10 also provides the additional function of protecting the pressure terminal 84 from damage due to arcing. It will be observed that similar to contact 34, the protective means 110 is in metallic contact with the conductive sleeve member 30. Thus, protective means 110 functions as arcing contacts for the main contact 34. Upon insertion of the probe, arcing occurs between conductor 20 of the probe and the protective means 110, with very little arcing occurring when conductor 20 engages contact 34, as contact 34 is effectively connected in parallel with the protective means 110. Similarly, upon breaking the electrical circuit, very little arcing occurs between conductor 20 and contact 34, as the current is transferred to the protective means 110, with the major arcing occurring as conductor 20 leaves protective means 110. Since protective means 110 performs the function of arcing contacts, a coating or insert of arc resistant material, such as insert 130, may be disposed at the end of protective means 110 which is adjacent end 92 of the quench tube 36. Suitable arc resisting materials for example are electrically conductive alloys containing tungsten.

The resilient or biasing means for spacing the segments 112 and 114 of the protective means 110, instead of being metallic spring members, may be a thin wall extension of the quench tube 36, about which the protective means 110 is disposed. This embodiment of the invention is shown in FIGS. 3 and 4, with like reference numerals in FIGS. 1, 2, 3 and 4 indicating like components, and like reference numerals with a prime mark indicating like functions but modified structures.

More specifically, FIG. 3 is an elevational view, in section, of an electrical connector assembly 10' having a cable connector 12, as hereinbefore described relative to FIG. 1, and a bushing assembly 14, similar to bushing assembly 14 in FIG. 1 except for having a new quench tube 36' and a new protective means 110. FIG. 4 is a perspective view of quench tube 36' and protective means 110.

Quench tube 36 is similar to quench tube 36, hereinbefore described, except modified to include a thin walled extension 136, best show in FIG. 4. Extension 136 has an aperture which is an integral continuation of the aperture in the main body portion of the quench tube.

The length dimension of extension 136 is substantially the same as the longitudinal length dimension of the protective means 110, and its wall thickness is selected such that it will deform when squeezed by the protective means 1 10'.

The protective means 110' includes first and second segments 112' and 114, which are similar to segments 112 and l 14 shown in FIG. 1, except having an aperture 122' when assembled which accepts the outer diameter of the extension 136 on the quench tube 136, which automatically sets and provides the desired predetermined air gap between the aligned faces or poles of the segments 112 and l 14'.

In this embodiment, additional biasing or resilient means are not required between the poles of the segments, since they are spaced apart by the extension 136 on the quench tube 36'. However, alignment means, such as means 142 and 144, may be provided between the segments to hold them in assembled relation while they are being advanced into the desired longitudinal position within the conductive sleeve or tubular member 30.

In the operation of the electrical connector assembly 10', if the connector 12 is assembled with the bushing assembly 14' when there is a low impedance fault in the load circuit, the segments 112 and 114' will be attracted to one another and close the gap 120 between the poles, squeezing the extension 136 from opposite sides, to deform the extension and cause it to prevent the removal of the probe 23. This is unlike the embodiment of FIG. 1, wherein the protective means itself contacted the shoulder 29 to block the removal of the probe. Also, in this embodiment of the invention, the protective means being lined with the extension 136, does not function as arcing contacts for the contact member 34. An arc is drawn between pressure terminal 84 of contact 34 and conductor 20, which is immediately squeezed between the snuffer rod 24 and the extension 136 on the quench tube 36'.

In order to facilitate the flexing or deformation of the extension 136 of the quench tube 36, under the urging influence of the electromagnet or protective means 110', a plurality of Iongitudinal slots, such as slots 148 and 150, may bedisposed in the extension 136, starting at the extreme end 152 of the extension and extending for a predetermined distance toward the main body portion of the quench tube, such as about onehalf the overall length of the extension.

The longitudinal slots, such as slots 148 and 150 in addition to adding mechanical flexibility to the extension, also promote the extinction of an are drawn between conductor 20 and contact 34. The slots allow the segments 112 and 114' to function as arcing contacts, as the current flow in the arc transfers from the contact 34 to the segments of the electromagnetic clamping means upon withdrawal of the connector 12 from the bushing 14. Also, the current flow in the arc is broken into as many paths as there are slots. Thus, the slots break up the are into a plurality of smaller, lower energy arcs, cooling the arcs and making it easier to extinguish them as they are drawn through the slots in the arc extinguishing material, and eventually squeezed between the non-slotted portion of the extension 136 and the snuffer rod 24 on the end of the probe 23.

While the embodiments of the invention hereinbefore disclosed have illustrated the step or shoulder 29 in the probe 23 as being in the electrically conductive portion of the probe, the step or shoulder may also be disposed in the snuffer rod, if desired. FIG. illustrates this embodiment of the invention, with like reference numerals in FIGS. 3 and 5 indicating like components, and like reference numerals with a double prime mark indicating like functions with modified structures.

More specifically, FIG. 5 illustrates an electrical connector having a bushing assembly 14" similar to bushing assembly 14 of FIG. 3, except with a modified contact 34", and with a connector 12" similar to connector 12 of FIG. 3, except with a modified probe 23".

Probe 23" is modified to step outwardly from the first or smaller diameter 25 to the larger diameter 27 in the snufi'er rod 24", instead of in the electrical conductor Thus, conductor 20 has substantially the same diameter 25 throughout its length within the cavity 18 of the connector 12", and pressure terminal 84" is modified to make electrical contact with this smaller diameter of contact 20", while being sufficiently flexible to pass the larger diameter 27 of the snuffer rod 24". Thus, the shoulder 29" on the snuffer rod 24" is caught and held by the protective means 110'. When the protective means 1 10 is actuated by fault current, to prevent the removal of the probe when it is attempted to be blown back by the gas pressure produced within the connector assembly 10" by fault current flow.

In summary, there has been disclosed new and improved electrical connector assemblies of the plug-in, loadbreak type, which automatically prevent blow-back of the cable connector on fault closure, by utilizing a magnetic clamp disposed to prevent removal of the cable conductor from the bushing when a predetermined current magnitude is exceeded. The magnetic clamp may be provided at a low cost, it is easily replaced if damaged, and it functions automatically when there is danger of blow-back.

In addition to providing the blow-back protective function, the magnetic clamp also functions, in certain embodiments, as arcing contacts, which prevent damage to the main bushing contact, and in other embodiments, in combination with a slotted extension on the quench tube, it functions to break up the are into a plurality of smaller lower energy arcs, promoting quick extinction of the arc with a minimum erosion of the arc extinguishing material, and with lower pressures due to less heat and a smaller volume of ionized gases.

1 claim as my invention:

1. An electrical connector assembly comprising:

a cable connector having a probe which includes a first electrical contact,

a bushing assembly having a second electrical contact,

said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts,

and magnetically responsive protective means disposed in said bushing assembly, having an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation,

the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude, preventing de-coupling of said cable connector from said bushing assembly.

2. The electrical connector assembly of claim 1 wherein the portion of the probe which extends through and past the aperture in the protective means increases in diameter to provide a shoulder which cooperates with the protective means when its aperture has reduced its dimensions, to prevent de-coupling of the cable connector from the bushing assembly.

3. The electrical connector assembly of claim 2 wherein the shoulder is formed in the first electrical conductor.

4. An electrical connector assembly comprising:

a cable connector having a probe which includes a first electrical contact, a bushing assembly having a second electrical contact, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts,

protective means disposed in said bushing assembly, having an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation,

the portion of the probe which extends through and past the aperture in the protective means increases in diameter to provide a shoulder which cooperates with the protective means when its aperture has reduced its dimensions, to prevent de-coupling of the cable connector from the bushing assembly,

the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude,

preventing de-coupling of said cable connector from said bushing assembly, and cooperative insulating rod and tube members disposed to squeeze an are formed between the first and second electrical conductor means, with the insulating rod being part of the probe'assembly and fixed to the end of the first electrical conductor, and the insulating tube member being disposed in the bushing assembly.

5. The electrical connector assembly of claim 4 wherein the shoulder is formed in the first electrical conductor.

6. The electrical connector assembly of claim 4 wherein the shoulder is formed in the insulating rod member.

7. An electrical connector assembly comprising:

a cable connector having a probe which includes a first electrical contact, a bushing assembly having a second electrical contact, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts,

and protective means disposed in said bushing assembly, having an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation,

the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude, preventing de-coupling of said cable connector from said bushing assembly, said protective means including at least two metallic segments spaced by biasing means, which provide an aperture having a predetermined diameter, with the mutual attraction of the segments overcoming the biasing means at a predetermined current flow, to reduce the spacing between the segments and the dimensions of the aperture.

8. An electrical connector assembly, comprising:

a cable connector having a probe which includes a first electrical contact,

a bushing assembly having an aperture with a second electrical contact disposed therein,

said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between the first and second electrical contacts,

means for extinguishing an are between the first and second electrical contacts, including an insulating rod fixed to the end of the first electrical contact, and an insulating tubular member disposed at the entrance end of the aperture of said bushing assembly, through which the probe passes in making and breaking the electrical connection, and a metallic, magnetic clamp disposed between the second electrical contact and said insulating tubular member, having an aperture therein which accepts the probe of the cable connector when it is plugged into the bushing assembly,

said magnetic clamp being responsive to the magnitude of current flowing through the electrical connection, reducing the dimensions of its aperture when a predetermined current magnitude is exceeded, to prevent removal of the probe from said magnetic plant.

9. The electrical connector assembly of claim 8 wherein the portion of the probe which extends past the aperture in the magnetic clamp increases in diameter to provide a shoulder which cooperates with the clamp when it reduces the dimension of its aperture, to prevent withdrawal of the probe from the magnetic clamp.

10. The electrical connector assembly of claim 9 wherein the shoulder is formed in the first electrical conductor.

11. The electrical connector assembly of claim 9 wherein the shoulder is fonned in the insulating rod member.

12. The electrical connector assembly of claim 8 including metallic means interconnecting the magnetic clamp and the second electrical contact, with the magnetic clamp providing arcing contacts for the second electrical contact.

13. The electrical connector assembly of claim 8 wherein the insulating tubular member includes a tubular extension on one end thereof which extends into the aperture of the magnetic clamp, with the magnetic clamp deforming the tubular extension to prevent decoupling of the probe from the bushing assembly when the predetermined current magnitude is exceeded.

14. The electrical connector assembly of claim 13 wherein the tubular extension on the insulating tubular member defines at least one longitudinal slot which starts at the end of the tubular extension.

15. The electrical connector assembly of claim 14 including metallic means interconnecting the magnetic clamp and the second electrical contact, with the magnetic clamp providing an arcing contact for the second electrical contact.

16. An electrical connector assembly, comprising: a plug-in cable connector including insulating means defining a cavity, and having a probe extending outwardly from the bottom of the cavity, said probe including a first electrical conductor, and an insulating rod formed of an arc extinguishing material fixed to the outwardly extending end of said first electrical conductor,

a bushing assembly including an insulating body member having first and second ends, an aperture which starts at its first end, a second electrical contact disposed in the aperture with its end facing the first end of the insulating body member, including a pressure terminal adapted to engage the first electrical conductor of said probe, and a tubular insulating member formed of arc extinguishing material disposed in the aperture at the first end of said insulating body member,

and magnetic clamp means disposed in the aperture of said insulating body member, adjacent the pressure terminal of said second electrical conductor, said magnetic clamp means including at least two metallic segments which are spaced apart by biasing means, and which overcome the biasing means to reduce the spacing, and the dimensions of an aperture therethrough, when a predetermined current magnitude through the first and second electrical conductors is exceeded,

said probe having at least first and second different diameters, with the first diameter being smaller than the second, providing a shoulder between the two diameters which passes through the aperture in the magnetic clamp means when the cable connector is plugged into the bushing assembly, and with said magnetic clamp means cooperating with said shoulder to prevent removal of the probe from the magnetic clamp means when the magnetic clamp means has reduced the dimensions of its aperture in response to current flow.

17. The electrical connector assembly of claim 16 wherein the shoulder in the probe is formed in the first electrical conductor.

18. The electrical connector assembly of claim 16 wherein the shoulder in the probe is formed in the insulating rod.

19. The electrical connector assembly of claim 16 wherein the tubular insulating member includes a tubular extension which enters the aperture in the magnetic clamp means.

20. The electrical connector assembly of claim 19 wherein the tubular extension includes at least one longitudinal slot therein. 

1. An electrical connector assembly comprising: a cable connector having a probe which includes a first electrical contact, a bushing assembly having a second electrical contact, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts, and magnetically responsive protective means disposed in said bushing assembly, havinG an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation, the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude, preventing de-coupling of said cable connector from said bushing assembly.
 2. The electrical connector assembly of claim 1 wherein the portion of the probe which extends through and past the aperture in the protective means increases in diameter to provide a shoulder which cooperates with the protective means when its aperture has reduced its dimensions, to prevent de-coupling of the cable connector from the bushing assembly.
 3. The electrical connector assembly of claim 2 wherein the shoulder is formed in the first electrical conductor.
 4. An electrical connector assembly comprising: a cable connector having a probe which includes a first electrical contact, a bushing assembly having a second electrical contact, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts, protective means disposed in said bushing assembly, having an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation, the portion of the probe which extends through and past the aperture in the protective means increases in diameter to provide a shoulder which cooperates with the protective means when its aperture has reduced its dimensions, to prevent de-coupling of the cable connector from the bushing assembly, the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude, preventing de-coupling of said cable connector from said bushing assembly, and cooperative insulating rod and tube members disposed to squeeze an arc formed between the first and second electrical conductor means, with the insulating rod being part of the probe assembly and fixed to the end of the first electrical conductor, and the insulating tube member being disposed in the bushing assembly.
 5. The electrical connector assembly of claim 4 wherein the shoulder is formed in the first electrical conductor.
 6. The electrical connector assembly of claim 4 wherein the shoulder is formed in the insulating rod member.
 7. An electrical connector assembly comprising: a cable connector having a probe which includes a first electrical contact, a bushing assembly having a second electrical contact, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between said first and second electrical contacts, and protective means disposed in said bushing assembly, having an aperture through which the probe of said cable connector extends when said cable connector and bushing assembly are coupled in an assembled relation, the dimensions of the aperture in said protective means being responsive to the magnitude of the current flowing through said electrical connection, with the dimensions of the aperture being reduced when the current exceeds a predetermined magnitude, preventing de-coupling of said cable connector from said bushing assembly, said protective means including at least two metallic segments spaced by biasing means, which provide an aperture having a predetermined diameter, with the mutual attraction of the segments overcoming the biasing means at a predetermined current flow, to reduce tHe spacing between the segments and the dimensions of the aperture.
 8. An electrical connector assembly, comprising: a cable connector having a probe which includes a first electrical contact, a bushing assembly having an aperture with a second electrical contact disposed therein, said cable connector and bushing assembly having complementary surfaces, enabling said cable connector to be plugged into said bushing assembly and form a sealed electrical connection between the first and second electrical contacts, means for extinguishing an arc between the first and second electrical contacts, including an insulating rod fixed to the end of the first electrical contact, and an insulating tubular member disposed at the entrance end of the aperture of said bushing assembly, through which the probe passes in making and breaking the electrical connection, and a metallic, magnetic clamp disposed between the second electrical contact and said insulating tubular member, having an aperture therein which accepts the probe of the cable connector when it is plugged into the bushing assembly, said magnetic clamp being responsive to the magnitude of current flowing through the electrical connection, reducing the dimensions of its aperture when a predetermined current magnitude is exceeded, to prevent removal of the probe from said magnetic plant.
 9. The electrical connector assembly of claim 8 wherein the portion of the probe which extends past the aperture in the magnetic clamp increases in diameter to provide a shoulder which cooperates with the clamp when it reduces the dimension of its aperture, to prevent withdrawal of the probe from the magnetic clamp.
 10. The electrical connector assembly of claim 9 wherein the shoulder is formed in the first electrical conductor.
 11. The electrical connector assembly of claim 9 wherein the shoulder is formed in the insulating rod member.
 12. The electrical connector assembly of claim 8 including metallic means interconnecting the magnetic clamp and the second electrical contact, with the magnetic clamp providing arcing contacts for the second electrical contact.
 13. The electrical connector assembly of claim 8 wherein the insulating tubular member includes a tubular extension on one end thereof which extends into the aperture of the magnetic clamp, with the magnetic clamp deforming the tubular extension to prevent decoupling of the probe from the bushing assembly when the predetermined current magnitude is exceeded.
 14. The electrical connector assembly of claim 13 wherein the tubular extension on the insulating tubular member defines at least one longitudinal slot which starts at the end of the tubular extension.
 15. The electrical connector assembly of claim 14 including metallic means interconnecting the magnetic clamp and the second electrical contact, with the magnetic clamp providing an arcing contact for the second electrical contact.
 16. An electrical connector assembly, comprising: a plug-in cable connector including insulating means defining a cavity, and having a probe extending outwardly from the bottom of the cavity, said probe including a first electrical conductor, and an insulating rod formed of an arc extinguishing material fixed to the outwardly extending end of said first electrical conductor, a bushing assembly including an insulating body member having first and second ends, an aperture which starts at its first end, a second electrical contact disposed in the aperture with its end facing the first end of the insulating body member, including a pressure terminal adapted to engage the first electrical conductor of said probe, and a tubular insulating member formed of arc extinguishing material disposed in the aperture at the first end of said insulating body member, and magnetic clamp means disposed in the aperture of said insulating body member, adjacent the pressure terminal of said second electrical conductor, said magnetic clamp means including at least two mEtallic segments which are spaced apart by biasing means, and which overcome the biasing means to reduce the spacing, and the dimensions of an aperture therethrough, when a predetermined current magnitude through the first and second electrical conductors is exceeded, said probe having at least first and second different diameters, with the first diameter being smaller than the second, providing a shoulder between the two diameters which passes through the aperture in the magnetic clamp means when the cable connector is plugged into the bushing assembly, and with said magnetic clamp means cooperating with said shoulder to prevent removal of the probe from the magnetic clamp means when the magnetic clamp means has reduced the dimensions of its aperture in response to current flow.
 17. The electrical connector assembly of claim 16 wherein the shoulder in the probe is formed in the first electrical conductor.
 18. The electrical connector assembly of claim 16 wherein the shoulder in the probe is formed in the insulating rod.
 19. The electrical connector assembly of claim 16 wherein the tubular insulating member includes a tubular extension which enters the aperture in the magnetic clamp means.
 20. The electrical connector assembly of claim 19 wherein the tubular extension includes at least one longitudinal slot therein. 